The invention relates to a heat shield with acoustic insulation. Such heat shields are used, e.g., in motor vehicles, in order to provide a shield between the exhaust muffler (along with other heat-conducting parts of the exhaust system, such as the catalytic unit) and the vehicle body, thereby preventing any appreciable radiated heat from impinging on the vehicle body, and at the same time providing effective acoustic insulation.
According to the state of the art it is known to use an aluminum sheet as a heat shield, disposed adjacent to the heat source (e.g. an exhaust pipe), at a location above the heat source (e.g. particular between said exhaust pipe and the vehicle body). Such shields may have a three-dimensional curved shape, e.g. generally the shape of a cylindrical segment. Further, the sheet may be corrugated or textured. An aluminum sheet of this type has the drawback that, while providing good heat shielding, its acoustic insulation performance is in the range of unsatisfactory to nonexistent.
It is further known to provide acoustic insulation in the form of a mineral foam, disposed on the back side of a heat shield sheet, wherewith in order to achieve a specified level of acoustic insulation the sheet is perforated with appropriate openings.
However, such a device has the disadvantage that the perforations sacrifice most of the heat shielding performance, because most of the [irradiated] heat is capable of penetrating the perforations. A further disadvantage is that the acoustic insulation, being disposed on the back side of the shield sheet, performs only poorly.
Also known is the application of an acoustic insulation layer comprised of mineral material, e.g. mineral foam, to the inner side of the aluminum sheet, i.e. the side facing the heat source.
This is attended by the disadvantage that the thermal stress on the mineral insulation is substantially increased, and the metal shield sheet can no longer reflect sufficient heat back toward the irradiating source. As a result, the shielding performance of the device is inadequate, since a substantial part of the heat penetrates the shield in the direction of the vehicle body, rather than being reflected away.